"My uncle missed the deer, I was sure. I could see no blood": Hisham Matar at his home in London. Photograph: Katherine Rose for the Observer

I can pinpoint the exact moment when I first began to think about what profession I should go into. It was 1978, I was seven and had just been handed over by the women of my family to the earnest and self-important gatherings of the men. I was no longer the responsibility of my aunts and older female cousins. I was now a man. This was a tragedy. Women were fun. They produced things: feasts and gossip. They sang, played the goblet drum and danced that miraculous Libyan dance where the hips seem to move independent of the body. They painted their hands and feet with henna. They cut up aloe plants to extract the slimy stuff for their skin. They were like mad scientists, whisking up egg, honey, olive oil and God-knows-what to bathe their hair in the mixture. They plotted social manoeuvres, planned parties and funerals, and had an opinion about everything. As a young boy in Libya it was hard to escape the conclusion that the women were the most feeling and most functional part of society.

As part of the ritual of becoming a man, my maternal uncle, a judge, and his four sons, each older than me, took me deer hunting. I had heard about these trips before, and once saw the Range Rover return caked in yellow sand. There were carcasses roped to the roof. One deer had its head over the rail of the roof rack, its mouth open and, like an offering, a bright purple tongue hung out of it.

Neither of my parents was enthusiastic about me going on the hunt, but they let me. My uncle, his sons and I set off late one morning. Soon we were out of Tripoli, going off-road, entering the vast Libyan Desert. My uncle was driving. On more than one occasion the wheels lost contact with the ground. We were running late as we had to get to the oasis before nightfall. I sat cramped in the back corner. My responsibility was to hold on to a square cardboard box, the size of a small radio, which was packed with shotgun shells. They had bright-red plastic bodies and shiny brass heads. They looked like they might be filled with chocolate.

Cousin Ahmed, who was sitting beside me, his arm and shoulder over mine, said, "I keep telling Baba to switch to rifles, but he insists shotguns are better."

"They are safer," Uncle said, wrestling with the steering wheel.

"And louder," Cousin Mansur, the eldest, said. He was sitting in the front, beside his father.

Then my cousins began talking, slowly and loudly, about the hunt. I knew that this was part of my initiation into their secret world. Perhaps for this reason, I did not listen very attentively. But I do recall something being said about mercy, about how before firing at a deer one must be absolutely certain of killing it, that any hesitation or doubt can be dangerous, that when you pull the trigger you must be confident of killing the beast. But if you wounded the animal, you must wound it enough to prevent it from running away.

"That's right," my uncle confirmed. "Worst thing would be for it to run and hide, to die in slow agony."

Someone said that it would be at least another eight hours before we reached our destination. The sun was already in the middle of the sky, its heat pressing down through the roof. I looked out of the window. The line where the sky met the earth was melting in the distance. For some reason, I began to wonder what I should be, what I should spend the majority of my life doing. I was seven, but this felt to be an immensely important and urgent decision to make. I definitely did not want to be a judge like my uncle. There was something about him that was distant, which I could not help but associate with his profession. Nor did I want to be, like many of my relatives, a businessman, or, like my favourite uncle, a diplomat. I wanted to make something. And I did not get the impression that businessmen and diplomats made anything.

I had recently watched on television a man conduct a symphony. I think he was Italian. He had the strong features and intensity of Victor de Sabata. Although I did not understand the music – or perhaps it was exactly because I did not understand the music – the performance made a deep impression on me. Sitting in the back of my uncle's Range Rover, as the wheels yawned in the sand and pummelled the rocks, I thought to myself: how fantastic it must be to be a maestro.

In those days, I could not care less for classical music: western or Arabic. I liked Boney M, the Bee Gees and that horrible West German pop band Genghis Khan. I spent days copying their dance moves. What had appealed to me about the conductor, however, was the seeming scale and mystery of his passion. Although, of course, I could not then have put it in these terms, I realise now that I took him, his very form and function, to be evidence of the existence and merit of art and the artistic endeavour. In that moment, as we drove through the desert, what excited me was the possibility – but also, strangely, the conviction – that I might one day be an artist. As baffling as the feeling was, I knew it to be something to celebrate and, at the same time, something to keep and protect, like a tender secret.

Night did fall before we arrived. The world outside was divided into two plains: the ground was a black so vacant you wondered if it was still there, and the sky, which was a dark luminous blue, was dusted with stars that burned too brightly. My cousins were completely silent now. In front of the car the headlights lit a small pool of light. It seemed breathless. And behind us a red dust-cloud hovered.

Then there was doubt about the direction we were travelling in. We stopped. A watch and a compass were consulted, the matter settled, and we set off again. Nonetheless, everyone in the car kept quiet – which did not suggest confidence. Some time later, the car began descending into a sort of dip or a valley. Someone laughed. Cousin Ahmed asked me to look, pointing ahead. Everyone now was asking me to look. At first I could not see it. Then there it was, a silver coin in the distance – the oasis, finally.

THERE WAS A LOT of laughter as we put up the tent and lit a fire. Cousin Mansur, the eldest, was carried by his brothers and almost thrown into the water. I watched my uncle place on a rug beside the fire the five shotguns. He carefully wrapped them in a cloth. When I handed him the box of shells, he smiled: "I know you are tired, but you will see tomorrow, it's worth it."

We had to be up in a few hours, before dawn, before the deer came to drink. Several of my cousins asked if I was cold. I said I was fine, but one of them laid another blanket on me, its weight settling evenly. Lying in the open, under the packed sky, I felt anxious, exposed and oddly unprepared. I wondered about my choice to be a conductor. I decided it was not for me.

My uncle woke me up. He had his index finger against his lips. The sun was not visible yet, but it lit the sky a pale blue. "Keep quiet," Uncle whispered. "Keep absolutely quiet."

On top of the hill, on the opposite side of the spring, there were three deer contemplating whether it was wise to descend. They looked at us, looked away, paced back and forth. We watched them. My uncle had a shotgun in his hand, so did each of my four cousins. I copied my uncle and lay on my stomach, watching the three deer. They eventually began to descend, followed by more deer: big ones and young ones. They all looked not so much wary as shy. They stood by the edge of the water, their dark eyes blinking, and slowly lowered their heads. Their brown noses disturbed the glassy water.

More and more deer descended. I thought there must have been 100 or more but, later, driving back, my uncle and cousins insisted that there could not have been more than 20. They formed a crescent, facing us. Suddenly, a shot exploded. It was louder than anything I had ever heard. It belonged to my uncle, because he was recharging his gun now, slotting in two fresh shells. The deer scattered, chasing one another up the hill. They seemed almost relieved, as if glad their doubts were finally confirmed. I, too, was relieved for I could not see any of them down. My uncle had missed, I was sure. And now his sons were firing like maniacs, and yet still I could see no blood. But then, after the firing stopped and the dust from all the running settled, someone shouted, "Three." Then another said, almost irritated at the error, "No, four." Now I could see the figures, their colour only slightly darker than the desert floor.